After all, they’ve been living, breathing and practising it all their lives, having inherited the famous musical legacy of one of Brit folk’s most revered families, The Watersons. Indeed, Marry was just 10 when she made her stage debut, followed soon afterwards by her first recording with her mother Lal Waterson and aunt Norma Waterson. After several years sowing his wild musical oats, her brother Oliver finally made his own entree into the family business in 1996, collaborating with Lal on Once In A Blue Moon, an album that has subsequently acquired an extraordinary cult status which grows by the day and has had a profound influence on a thriving new generation of folk artists.

Yet it would be a grave mistake to assume Marry and Oliver are shaped exclusively by their rich folk heritage. Oliver’s style evolved in his teens when, delving under a bed he made an interesting discovery – his uncle Martin Carthy‘s Fender Telecaster electric guitar – which he appropirated to become a bedroom guitar hero, playing along with his beloved Pink Floyd records. It led him not to folk music but to strutting his stuff in blues and rock covers bands with names like Son Of God’s Mate and Vampire Prawns. Ask Oliver his favourite tracks of all time and he’ll reel off various unexpected cuts by Madness, Thin Lizzy, The Beat and Hazel O’Connor…and the complete works of Pink Floyd. Marry’s influences are no less eclectic, encompassing everything from Mozart and Billie Holiday to Harry Nilsson and Bad Company’s Gone Gone Gone (“which I discovered in my teens as a biker chick!”)

Marry Waterson & Oliver Knight

They are, then, an unusual pair, this brother and sister act. They have an intuitive partnership but it was a long time in gestation before the sudden explosion of beautiful, evocative, mysterious songs which have blossomed on their debut album together, an album born of circumstance rather than design. Marry’s singing had been on the back burner since she left the family farmhouse in Flyingdales Moor near Robin Hoods Bay where the whole Waterson clan then lived (and were rather amusingly known locally as “the hippies”) to pursue a career in graphic design, which escalated into sculpture, renovating houses and raising a family. Oliver, meanwhile, had been working as a gardener, but his inventive input on the Once In A Blue Moon and A Bed Of Roses albums with his mother Lal alerted the wider world to his skills and many of folk’s leading figures started beating a path to his Panda Sound studios to engage him as arranger, producer and sound engineer.

Lal Waterson’s death in 1998 initially scuppered any thoughts Marry may have had of singing seriously again. “Mum always encouraged me to sing in the house, in the car or wherever we were and I always enjoyed the physical act of singing….in the first week after she died I could listen to her music, but after two weeks I couldn’t touch it. I couldn’t be around it and it took me nine years to be able to sing the music that had been the soundtrack to my life.”

The breakthrough came when the Waterson family were booked to appear at London’s Royal Albert Hall in 2007. When, accompanied by Olly, Marry stepped forward to sing one of her mum’s most celebrated songs, Fine Horseman, there wasn’t a dry eye in the house and a queue of people collared her afterwards to tell her she’d turned them into emotional wrecks (“how do you think I felt?” she replied). They all had another question too: when was she going to record an album?

A Lal tribute show at London’s Cecil Sharp House later that year once more pitched Marry and Olly on stage together and the creative vein they’d both suppressed for so long was finally unlocked. New songs flooded out of them and they spent more and more time crafting them in Olly’s studio until one day, much to their own amazement, they realised they had an album.

Their mother’s influence is self-evident – one of the tracks Angels Sing is not only about Lal but includes some of her own lines, as does Rosy – yet it has a unique, genre-defying atmosphere entirely of its own. “Marry doesn’t have a musical training or any grounding in how things should be done so there are no rules and that creates its own quirkiness – something that was also there with mum,,” says Olly. “I just sing whatever comes into my head and Olly helps me structure it,” agrees Marry. “Songs are about personal experience, about childhood memories, love, death, the various things we all experience…”

They include Curse The Day, which tackles the thorny subject of PMT, while the poetic vignettes of Secret Smile and The Gap encompass Perry Como, Doris Day and Jesus and the evocative imagery of Yolk Yellow Legged invokes a “buddleia day in the morning’s prime”, a “balletic Nureyev flair” and “beaded cobwebs on lollypop trees”. Magical stuff.

Yolk Yellow Legged was co-written by James Yorkston, who also duets with Marry on the track, while Kathryn Williams (who, like Yorkston, performed at the 2007 Lal tribute concert) co-wrote Father Us and Secret Smile, singing harmonies on both (repaying Marry’s favour of singing on the Lal-inspired Winter Is Sharp on the Williams album The Quickening). Marry and Olly’s cousin Eliza Carthy is also prominent, playing fiddle on a couple of tracks and singing lead on The Loosened Arrow, while Reuben Taylor’s piano adds further textures, notably setting the winsome, McGarrigle-esque tone of Run To Catch A Kiss.

“I can’t deny I’ve been influenced by mum’s writing,” says Marry. “She’d always push things a little bit further and she taught me not to accept your first go and look deeper until you find less obvious ways to say something… We owe a debt to our family’s wall of sound. It’s our heritage and it’s definitely in there, but we have our own style and we’re not beholden to it.”

It took them forever to get it together but – organic, original, vivid and gloriously real – the Marry Waterson-Oliver Knight partnership is set to carve its own place in the family legend.